The present invention relates to a gas turbine engine, and in particular to such an engine having improved compressor performance during periods of transient engine operation.
A current problem existing in turbomachinery, such as, for example, gas turbine compressors, relates to transient thermal response during periods of engine operation known as throttle burst and throttle chop. Throttle burst is the engine speed transition from idle to full power whereas throttle chop is the speed transition by which the engine is brought back to idle. During these periods of transient engine operation, large radial excursions occur in both stator and rotor components. To prevent interference between the compressor stator and rotor during these transient excursions, clearances are provided between the stator and rotor blades. These clearances in typical compressors are undesirably large during both transient and nontransient operation, thus, adversely affecting compressor efficiency and stall margin. More particularly, the outer casing wall of a typical gas turbine compressor stator is relatively thin walled metal, and it responds rapidly to temperature changes during periods of transient engine performance such as throttle burst (advanced or heavy throttle) or throttle chop (reduced throttle).